A Resistance Temperature Detector (RTD) senses an environmental temperature by detecting changes in the electrical characteristics of the sensing circuit in the RTD. The sensing circuit typically includes a metallic wire or metallic film with a known electrical resistance that changes depending on the temperature sensed by the RTD. This relationship between the electrical characteristics of the RTD and temperature change are known. Conventional RTDs include leads that are connected to an external device to provide an electrical signal to the RTD and to provide a conditioning circuit for electrical signal in response from the RTD so that it can be converted to a temperature measurement.
The conditioning circuit is used to linearize the response signal, attenuate the response signal, or both linearize and attenuate the response signal to provide a readable signal that can be correlated to a temperature. In some applications, it is desirable to read an RTD directly, without a conditioning circuit. Known RTDs produce a non-linear response or a have a large response to small inputs, which preclude direct reading of the output signal.
Accordingly, a need exists for an RTD that produces a linear response to temperature change that is within the scale of direct read instrumentation.